Method for recharging a bundling machine using a plastic film and bundling machine carrying out said method

ABSTRACT

Methods for recharging a machine which is used to pack groups of products with the aid of a plastic film wherein the film of a distributor reel is unwound, the film of a full reel is subsequently engaged into an injection device in such a way that said reel becomes a distributor reel in turn, then the empty distributor reel is replaced with a new full reel. While a reel is being distributed, the full reel is placed in the machine and the free end of the film connected to the full reel is maintained in a waiting position; when it is detected that the end of the film of the distributor reel has reached a predetermined position, the advance of the film of said reel is halted and the free end of the film connected to the full reel is driven in such a way that it becomes a distributor reel; while the full reel is being distributed, the empty distributor reel is replaced by a new full reel and the free end of the beginning of the film connected to said new reel is maintained, whereupon the previously mentioned cycle is resumed with a new reel when the final extremity of the film of the full reel which is being distributed reaches a predetermined position in the machine.

BACKGROUND OF THE INVENTION

This application is a 371 of PCT/FR02/01124, filed on Apr. 2, 2002.

The invention concerns improvements to the methods for reloadingmachines for packaging under plastic films, called bundling machines,through the use of such films. More particularly, it concerns a methodfor the quick loading of the film, and of machines that implement thismethod.

Packaging products under film is a popular technique, which allows anumber of products such as bottles, flasks, boxes, pots, or any othertype of objects to be grouped together. This technique makes it possibleto facilitate the transport of the products to the final destinationwhere the packaging is removed. Depending on the type of productspackaged, either the film is the only element of the packaging, or it isassociated with other elements such as boards, trays or other elementson which the products are arranged before being placed under film.

Machines intended for producing such packages are called bundlingmachines. They allow each group of products to be enclosed in a sectionof film. To that end, they include, on the one hand, a device forfeeding the groups of products to be packaged, such as a conveyor, andwhen appropriate a device for feeding associated elements, and on theother hand a distributor spool of film, a device for directing a firstend of the film toward each group of products to be packaged, devicesfor placing the film around the group of products in synchronism withthe advance of the film, devices for cutting the film when a section ofsufficient length is obtained and devices for closing the film aroundthe group of products.

In certain machines, the film used is of the heat shrinking type, andthe closure is accomplished by securing the film in a filmheat-shrinking tunnel. In other machines, the closure is accomplished byheat welding or gluing.

The device for directing a first end of the film toward the group ofproducts to be packaged, called film injection device, comprises forexample drive rollers between which the film is placed, and downstreamof these rollers, in the direction of advance of the film, a grippingdevice. The film, drawn between the rollers, is then gripped by thegripping device which directs it towards a conveyor or a table on whichthe group of products is placed, and which causes the film to undergo amovement allowing it to enclose the group of products. Furthermore, whena sufficient length of film to form a section allowing the group ofproducts to be enclosed is unwound, the film is cut so that a section ofthe film is completely available to package the group of products, andthe rest of the film can be used to package the subsequent groups ofproducts by repeating the above-mentioned operations.

Generally, and most particularly in the applicant's machines, thecutting means are associated with the injection device. In fact, saidinjection device comprises a first set of two rollers, called upstream,that are in tangential contact with each other, one of said rollersbeing the driver and the other driven, and a second set of two otherrollers, called downstream, identical to the first, also in tangentialcontact, with a drive roller and a driven roller, and the cutting meansare arranged between the two sets. The film is arranged so that itpasses between the two rollers of each set, and is drawn through as aresult of the pressure exerted between the two rollers of a same set.The cutting means are activated at appropriate times, in synchronismwith the cycle of the machine.

These machines require that the film distribution spool be replacedregularly, when all of the available length of film has been consumed.To that end, the machines include a storage device for a full standbyspool. Said standby spool is placed on this device while anotherdistributor spool is in the process of unwinding, and the change ofdistributor spool requires the packaging operations to be stopped inorder to heat-fuse the beginning of the film from this spool to the endof the film from the spool that is finished.

In the applicant's machines, by way of example, for the groups ofproducts of medium size that these machines package, the change ofdistributor spool takes place approximately every twenty minutes, andthe time of the shut-down and heat-fusing that this change involveslasts about twenty seconds if they are properly and efficiently carriedout. Therefore, approximately one minute of packaging time is lost everyhour because of the spool changes.

The preceding is true for films free of decorations that do not requireprecise positioning with respect to each other prior to the fusing.However, there are decorated films that require that the designs bealigned with the designs of the other one prior to fusing, whichprolongs the operations.

In fact, contrary to what one would believe, it is not the heat-fusingof the end of the film from the full distributor spool to the end of thefilm from the preceding spool that consumes the most time. On thecontrary, this operation makes it possible to gain time compared to theoperation consisting of paying out all of the preceding film beforereloading the machine with a new distributor spool. In effect, betweenthe zone of the machine where the distributor spool is placed and theinjection device, there is a compensation mechanism with a set ofcompensator rollers mounted on an articulated device, called “jumpingjack,” which allows the tension and unwinding speed of the film to beadjusted in order to take into account the fact that the packagingoperations are not carried out at a constant speed of unwinding of thefilm. The rollers of this mechanism cause the film to follow atrajectory that is relatively complex, and in any case non-linear,between the distributor spool and the injection device, so that if itwas necessary to allow all of the film to pay out, then, at the time ofreloading it would be necessary to position the new film correctly withrespect to the set of compensator rollers, then engage it in theinjection device by holding it correctly to prevent it from becomingcrumpled or laterally offset from said injection device. Theseoperations would take even more time to accomplish.

Thus, by heat-fusing the end of the preceding film to the beginning ofthe new one, the new one is immediately positioned correctly in thecompensation mechanism and becomes engaged in the injection device bybeing drawn by the remainder of the film from the preceding roll.

However, in order for the operation to be efficiently carried out, it isstill necessary for the operator to be present at the appropriate time,that is, when the end of the film is approaching.

To that end, the known machines include means of detecting the approachof the end of the film on the distributor spool that is unwinding. Saidmeans determine the length of film remaining on this spool and areactivated when it is less than a predetermined value. Indeed, because itis difficult to detect a length of film rolled onto a spool, the meansoften detect the remaining thickness of film on the distributor spool,which is a function of the remaining length.

These detection means can be coupled with means for warning the operatorwho, as soon as he is warned, takes over manual control of the machineand oversees the unwinding of the end of the distributor spool, thenstops the machine at the appropriate time and performs the heat-fusingoperation, restarts the machine, removes the empty spool and mounts afull standby spool. With this method of operation, if the operator isabsent when the warning is given, there is a risk that the distributorspool could unwind completely and the film totally released, involvingcompletely reloading the machine with the new film, that is, bypositioning it correctly with respect to the set of compensator rollers,then by engaging it again in the injection device.

Alternatively, the detection means can be coupled with means forstopping the film. This assumes that the operator takes over manualcontrol of the machine after the film is stopped, then oversees theunwinding of the end from the distributor spool, and stops the machineat the appropriate time to perform the heat-fusing operation, restartsthe machine, removes the empty spool and mounts a full standby spool.With this mode of operation, if the operator is absent at the time ofstopping, there is a risk of loss of additional time.

A purpose of the invention is to remedy these disadvantages.

SUMMARY OF THE INVENTION

According to the invention, a method for reloading a machine thatpackages groups of products with a plastic film intended for saidpackaging, said machine comprising on the one hand means of injectionand cutting the film, fed with film from a distributor spool locatedupstream in the direction of unwinding of the film of the injection andcutting means, and on the other hand means for storing a full spool,also upstream from the injection and cutting means, the method being ofthe type according to which, after detection of the approach of the endof the film on the distributor spool, various steps are implemented thatmake it possible to finish unwinding and emptying said spool, andengaging the film from the full spool into the injection means, so thatsaid injection means becomes the distributor in turn, then the spoolthat has been emptied is replaced by a new full spool, characterized inthat it consists of:

while a spool is in the process of distribution, placing a full spool inthe machine and keeping the free end of the start of the film on thisfull spool ready at the entrance of the injection and cutting means;

after having detected that the last part of the end of the film on thespool in process of distribution has reached a predetermined position inthe machine, stopping the advance of the film of this spool in theinjection and cutting means, and causing the free end of the filmconnected to the full spool to be drawn into said means, so that saidfull spool becomes the distributor;

while said full spool is in process of distribution, replacing the onethat was emptied with a new full spool, and maintaining at the entranceof the injection and cutting means the free end of the beginning of thefilm connected to said new spool, and starting this cycle over againwith the new spool, when in turn the end of the film of the spool inprocess of distribution reaches a predetermined position in the machine.

Thus, when the time comes to replace a spool, it is no longer necessaryto heat-fuse the end of the film from the spool that has just beenemptied to the beginning of the film on the full spool, and there istherefore no dead time during the replacement. Moreover, this mode ofoperation makes it possible to automate the replacement operation, thusreducing the demands on the operator who no longer has to actimmediately after the detection of approach of the end of the film of aspool. The operator then has all the time he needs to replace the spoolthat has just been emptied with a full one.

In one implementation, all of the film from the spool in process ofdistribution is allowed to pay out, and the predetermined position,which is detected, of the final end of this spool in the machine is theone where said film end leaves the injection and cutting means.

Thus, the free end of the beginning of the film on the full spool is ledinto the injection and cutting means when the film from the other spoolhas been completely consumed.

This implementation eliminates the fusing of one film to the other.

However, for each spool change this involves repositioning the film ofthe full spool at the entrance of the injection and cutting means andinto the compensation mechanism. This maneuver is quite conceivablewithin the time taken by a spool to completely unwind. However, it istedious and requires a great deal of the operator's time.

It is for this reason that, in a preferred implementation, when a spoolis finished, all of the film is not allowed to pay out but a portion ispreserved on the machine, and said portion is heat-fused to thebeginning of a full spool without stopping production. The end of theremaining portion of one film is therefore connected to the beginning ofthe film of a full spool, and it is thus the remaining part that drawsin the film from the full spool when the latter is placed in service.

To that end, according to another characteristic, the method consists ofmonitoring the passage of the last part of the end of the film from thespool in process of distribution, into the machine, into a predeterminedposition situated between the spool and the injection and cutting means;and

when the passage into this position is achieved, the advance of the filmfrom this spool into the injection and cutting means is stopped, inorder for a portion of film to remain between said film end and theinjection and cutting means, and the free end of the film connected tothe full spool is drawn into said means so that it becomes thedistributing spool;

removing the empty spool and putting a new full spool in place;

fusing the beginning of the film from the full spool to the end of theremaining part of the film from the spool that was removed.

Thus, apart from the removal of an empty spool and the installation of afull one, this implementation only requires fusing while productioncontinues, while a spool is being unwound. This allows time for theoperator to perform this operation with precision, even in the case offilms with decorative designs; moreover, the fusing has proper coolingtime and there is no longer any burdensome and complex operation ofreplacing the film, because the new one is drawn by a remaining part onstandby.

In one implementation, the detection of the predetermined position ofthe end of the film from the spool in process of distribution isperformed twice: a first time, when an approximate evaluation is made ofthe remaining length of film wound on this spool during thedistribution, then, when a predetermined value is reached, the advanceof the film from this spool into the injection and cutting means isstopped, the full spool is placed in service by causing the free end ofthe film from this full spool to be drawn into said injection andcutting means so that the latter spool becomes the distributor and theother one is stopped; and

a second time where the remaining length of film wound on the stoppedspool is precisely determined, after which:

a) if the length of film remaining on this stopped spool is sufficientto continue packaging groups of products,

the advance of the film from the other distributing spool into theinjection and cutting means is stopped, the free end of the filmconnected to the spool on standby is drawn into said means so that saidstandby spool becomes the distributing spool again, and

the passage is monitored of the upstream end of the film from the spoolin the machine into the predetermined position located between the spooland the injection and cutting means; and

when the passage into this position is reached, the advance of the filmfrom this spool into the injection and cutting means is stopped, thefree end of the film connected to the other spool is drawn into saidmeans so that it becomes the distributing spool again;

the empty spool is removed and a full spool is installed;

the beginning of the film from the full spool is fused to the end of theremaining part of the film from the removed spool, and [the operator]waits until the remaining length of film wound on the second spoolrequires another change of spool;

b) if the remaining length of film on this stopped spool is not enoughto continue packaging groups of products,

packaging is continued with the other spool until it is determined thatthe remaining length of film wound thereon requires another change ofspool, and during this time,

the end of the film from the first spool is drawn into the machine, insaid predetermined position located between the spool and the injectionand cutting means, and

the empty spool is removed and a full spool is put in place;

the beginning of the film from the full spool is fused to the end of theremaining film from the spool that has just been removed; and

the preceding operations are resumed by changing over from one spool toanother.

This mode of operation makes it possible to take into account thedifficulty in measuring the remaining length of film on a spool when itis unwinding, while avoiding losing film. It is easier to make anapproximate determination of the remaining length of film, for example,as indicated above, by evaluating the remaining thickness of film woundonto the spool. The evaluation can be only approximate, among otherreasons because of the vibrations of the machine and because there arecertain tolerances for the thickness of the film itself when it ismanufactured.

The approximate evaluation of the length of film remaining wound on thespool in process of distribution and the placement in service of thefull spool can be performed by the operator himself; however, to allowthe operator to perform other activities and to prevent the spool frombecoming completely unwound if the operator is absent, an automaticevaluation and automatic change-over are preferred.

The precise determination of the remaining length is easier when a spoolis stopped. Here also, this determination can be done by the operator,or it can be done automatically; this also applies to putting this spoolback in service in the event there is enough length still on it.

Finally, the monitoring of the passage of the upstream end of the filmfrom the spool in process of distribution in the machine, in saidpredetermined position, can be done by the operator or it can be doneautomatically.

According to another characteristic, the machine having a compensationmechanism between each spool and the injection and cutting means, thepredetermined position located between the spool and the injection andcutting means is monitored so that the advance from one spool in processof distribution is stopped when the end of the film carried by thisspool is between the spool and the corresponding compensation mechanism.In this way, after the fusing is performed, the remaining part of thefilm from a spool is used to engage the film from a new spool into thecompensation mechanism.

Thus, except for those rare cases in which a film comes off of thecompensation mechanism, which can occur following maintenance on themachine or an accidental tearing of a film, the film change operationstake very little of the operator's time, and he can thereforeconcentrate on other tasks required by the machine.

A device for implementing the method is characterized in that itcomprises two arrangements for alternatively distributing the film fromone spool and from the other to the injection and cutting means, whicharrangements include means, called drive and hold, arranged to hold thefree end of the film from the standby spool at the entrance of theinjection and cutting means, and to allow the film from the distributingspool to be drawn into the injection and cutting means.

According to another characteristic, the arrangements are identical.

In one implementation, the injection and cutting means are comprised ofa single device having rollers for driving the film at its entrance, thedrive and holding means are comprised of two different devices arrangedupstream from the entrance of the single injection and cutting device,and the machine is constructed so that, after having stopped the advanceof the film from one spool in process of distribution in the injectionand cutting means, the movement of the film in said means is reversed soas to release the free starting end, it is held with the correspondingdrive and holding device, and the free end is then drawn to thebeginning of the standby film toward the injection and cutting meanswith the other corresponding drive and holding device.

In one variation of implementation, the injection and cutting means arecomprised of two different devices, each of which receives the film froma spool, and each has at its entrance rollers for driving the film, andthe drive and holding means are comprised of drive rollers located atthe entrance of the injection and cutting devices, and the machine isconstructed so that the advance of the film from one spool in process ofdistribution into an injection and cutting device is stopped by stoppingthe rotation of these entry drive rollers, and the drawing of thestarting free end of the standby film, in the other injection andcutting device, is caused by placing these entry drive rollers inrotation.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will becomeapparent from the following description, with reference to the attacheddrawings in which:

FIG. 1 is a diagrammatic side view of a machine for the implementationof the method;

FIGS. 2 to 4 are diagrammatic side views of variations of embodiment ofthe part of the machine that makes it possible to use the film from onespool or the other.

DETAILED DESCRIPTION OF EXEMPLARY, NON-LIMITING EMBODIMENTS

The invention can be implemented on any known bundling machine. Thus,FIG. 1 diagrammatically illustrates the application of the invention toa machine for packaging groups of products 1, 2, 3, 4 using film 5 ofplastic material, which is made integral with a group of products aroundwhich it was wound through the use of any appropriate device 6, such asa heating tunnel when the plastic material used is heat-shrinkable, or aheat-fusing device or gluing device, as mentioned in the introduction.

The device of FIG. 1 is arranged to avoid having to reload thecompensator rollers for each spool change.

The film 5 is distributed from a distributor spool 7 and is directed tothe packaging zone 8 in which, in a known way, the groups of productsare transported, for example by means of a conveyor belt 9; they leavein the same way by means of another conveyor 10 that takes them to theclosing device 6.

In its path from the distributor spool 7 to the packaging zone 8, thefilm encounters guide devices such as the rollers 11, 12, 13 which, forsome of them 11, 12, are compensator rollers which, in addition to theirguide function, contribute to the adjustment of the tension of the filmas it is paid out of distributor spool 7. To that end, the rollers 11,12 are attached to movable mechanisms 14, 15 called jumping jacks.

Downstream from the guide devices 11, 12, the film 5 passes into adevice 16 which, according to the invention, can be made in severalvariations, which will subsequently be described in detail. Among otherthings, the device 16 has means 17 for the injection and cutting of thefilm.

In FIG. 1, the injection and cutting means are comprised of a singledevice, the structure of which, as is known, includes a first set,called upstream, of two rollers 18, 19, called injection, in tangentialcontact with each other, one of which, 18 for example, is the driver andthe other 19 is driven, and a second set, called downstream, identicalto the first, of two other rollers 20, 21, called pressure, also intangential contact, with one drive roller 20 and one driven roller 21.The film is arranged between the two rollers of each set, and is drivenby the pressure exerted between the two rollers of the same set.

In the area of the machine delimited between these two sets, means 17for the injection and cutting of the film include a device with a unit22 for cutting the film

The unit 22 for cutting the film, in order to make successive thesections thereof, is comprised in a known way by a sharp blade mountedon a bar 23 that can turn around its longitudinal axis as illustrated bythe arrow 24. The unit 22, here called the blade, and the bar comprisethe cutting device as such, which device is controlled by the machine'scontrol mechanism as a function of the desired length of sections offilm required to enclose the groups of products. To cut the film, thebar 23 is made to rotate so that the cutting edge of the blade passesthrough the thickness of the film while it is moving.

To that end, the bar 23 is connected to means to cause its rotation atthe appropriate times as the film advances in the machine. Thus, in oneimplementation, the means to cause the rotation are comprised of amotor, not shown, which can be sequentially controlled. In onevariation, the rotational movement is caused by a cam mechanismconnected, for example, to the drive mechanism of the drive rollers 18,20.

The means for causing the rotation of the bar can be connected theretodirectly or through a transfer mechanism.

Thus, in a known way, at the moment the film is cut, there are twoportions of film: a first portion 50 forming a section to package agroup 3 of products, and a second portion 51 integral with thedistributor spool 7. The first portion 50 is sent toward a group 3 ofproducts by means of a known movable guide device 25, and comprised forexample of a set of bars that come to grip the film at the outlet of thedownstream set of pressure rollers 20, 21, and causing it to follow anappropriate path, symbolized by the broken line 26, to enclose the group3 of products, while the second portion 51 continues to be drawn by theset of two injection rollers 18, 19 upstream from the means 17.

In a known way, the two sets are arranged so that, either they areassociated with means not represented such that, when the film has beencut, the end 27 of the second portion 51 of film, which is then locatedbetween the two sets, is directed between the two rollers 20, 21 of thedownstream set and is picked up by said rollers, before being gripped inturn by the guide device 25 which draws it toward the next group ofproducts, again following the appropriate path symbolized by the brokenline 26.

According to the invention, a full spool 70 is placed in the machine,while the film 5 from the distributor spool 7 is in the process ofunwinding, and the free end 52 of the film 53 connected to this fullspool is held on standby at the entry of the injection and cuttingmeans.

As illustrated, the machine has between this full spool 70 and the entryof the injection means, a second set of guide devices with the rollers110, 120, 130, 140, some of which 110, 120, are compensator rollers.These are then attached to movable mechanisms 150, 160 such as jumpingjacks.

According to the invention, the film 53 connected to the full spool isin two parts: a first part 54, which is the remaining portion of filmfrom a spool previously unwound in the place of the spool 70, and asecond 55 which is the beginning of the film originally placed on thefull spool.

The two parts 54, 55 are connected the each other by a weld 56 made byheat.

The weld 56 is therefore made at the end of the film from the spool thatwas previously in the place of the spool 70 and at the beginning of thefilm from the spool 70, when said spool is installed.

To accomplish the weld, means are provided, such as welding bars 28, 29,between which the film travels.

The first part 54 is routed along the second set of guide devices, withthe rollers 110, 120, 130, 140.

Consequently, the welding bars are placed between the spool 70 and thesecond set of guide devices, with its rollers 110, 120, 130, 140.

The free end 52 of the film 53 connected to this full spool 70 is heldat the entrance of the injection means 17 by drive and holding means,comprised in the example by the holding rollers 30, 31 a preferred formof embodiment of which is shown in FIG. 2.

The holding rollers 30, 31 are connected to motorized units, notvisible, which are designed to be turned on to drive the film 53 towardthe injection rollers 18, 19 to allow it to be picked up by saidrollers, and to be stopped in order to hold the film immobilized.

Indeed, with the configuration of FIG. 1 where it is the film from thespool 7 that is being driven by the injection rollers 18, 19, theholding rollers 30, 31 are in the stopped position.

In one implementation, the motorized units are designed to be turned onwhen the film 53 should be driven by the injection rollers, so that thefilm is driven by the holding rollers at the same speed as by theinjection rollers.

In one variation the holding rollers are self-disengaging with respectto the motorized units, and are disengaged when the film 53 is driven bythe injection rollers, so that in this configuration the film travelsfreely between the holding rollers.

The film 5 being unwound from the distributor spool 7 also passesbetween the welding bars 32, 33, in order to allow the spool change whenthe spool becomes empty, and between the holding rollers 34, 35 upstreamfrom the injection rollers 18, 19.

In a way identical to the rollers 30, 31, the holding rollers 34, 35 areconnected to motorized units, not visible, which are designed to startup to drive the film 5 toward the injection rollers 18, 19 in order toallow it be to be picked up by said injection rollers, and to be stoppedto hold the film immobilized.

With the configuration of FIG. 1 where it is the film from the spool 7that is driven by the injection rollers 18, 19, the holding rollers 34,35 are controlled or placed in a position such that the film from thespool 7 travels freely.

This form of embodiment, therefore, makes it possible to change filmwithout clearing either of the guide devices with the compensatorrollers.

Thus for example, considering the distributor spool 7, in process ofdistribution, it is only necessary to detect the position of the end offilm 5 on this spool before said end reaches the corresponding guidedevice 11, 12, 13, and when it reaches a predetermined position,manually or automatically to stop this spool, reverse the direction ofrotation of the injection rollers, pick up the film 5 with thecorresponding holding rollers 34, 35, and start the other film 53 towardthe injection rollers by means of the corresponding holding rollers 30,31.

Of course, as already explained, if after the film 5 is stopped, it isdetected visually or automatically that enough usable film remains, itis still possible to restart this film, manually or automatically, untilthe film effectively reaches the end of the spool, and ensure that itdoes not leave the respective guide device.

Next, the other spool is started and a new spool is put in place beforeproceeding with the welding.

In FIG. 2, a preferred form of embodiment is illustrated for the device16, including, among others, the means 17 for injection and cutting ofthe film.

The device 16 is represented in a position in which the film 53 is beingdriven and the film 5 is immobilized.

As already explained, the injection and cutting means include theupstream set of two injection rollers 18, 19, and the downstream set oftwo other pressure rollers 20, 21, as well as between these two sets,the device with a unit 22 for cutting the film, comprised of a sharpblade carried by the bar 23 that can turn around its longitudinal axis.

Two sets of holding rollers are arranged upstream from the injectionrollers 18, 19. The film 53 is positioned so as to pass between therollers 300, 310 of the first set, and the film 5 is positioned so as topass between the rollers 340, 350 of the second set.

One of the rollers 300, 350 of each of these sets is not completelycylindrical, but is provided with a flat surface 301, 351 parallel tothe axis of rotation of its respective roller 300, 350. The drivers, notshown, are designed to place the flat surface facing the other roller ofthe device when the film should be driven by the injection rollers, sothat the film runs freely in the gap that then appears between the tworollers.

Thus, in considering FIG. 2 where the film 53 is driven, the rollers300, 310 are stopped, with the flat surface 301 of the roller 300 facingthe roller 310; the rollers 340, 350 are stopped with their cylindricalpart in tangential contact to block the film 5.

When the film is changed, the direction of rotation of the injectionrollers 18, 19 is reversed to release the beginning, and the holdingrollers 300, 310 are simultaneously placed in rotation in order to clampthe film 53 and prevent it from being released from said rollers, afterwhich the holding rollers are stopped. Next, the rollers 340, 350 areplaced in rotation to drive the free end of the film 5 into theinjection rollers.

However, to prevent film from being released from the holding rollerswhen they are placed in rotation to drive the film toward the injectionrollers, it is best that the gap not appear during this phase. To thatend, the holding rollers of each device are arranged so that the lengthof the portion of film that could be taken between the injection rollersand the holding rollers is less than the perimeter of the cylindricalportion of each roller provided with a flat surface.

FIGS. 3 and 4 illustrate two variations of the device 16 in which theinjection means are comprised of two devices in parallel and in whichthe holding of a film in stopped position is accomplished by means ofthe injection rollers for the film in question, and it is provided, atthe outlet of the device 16, with means for directing the film beingunwound toward the movable guide device 25, comprised for example of theset of bars that grip the film at its exit from the upstream set ofpressure rollers 20, 21, and cause it to follow the appropriate pathsymbolized by the broken line 26, toward the packaging zone.

In FIG. 3, a first injection and cutting device includes injectionrollers 181, 191, the pressure rollers 201, 211, and a cutting unit 231;a second injection and cutting device includes the injection rollers182, 192, the pressure rollers 202, 212, and a cutting unit 232; themeans for directing the film in process of unwinding toward the movableguide device 25 are two belts 36, 37 each of which is located at theoutlet of an injection and cutting device to pick up the film exitingtherefrom.

A first belt 36 is, for example, stretched between a pressure roller 201of the first injection and cutting device and a tension roller 221; thesecond belt 37 is, for example, stretched between a pressure roller 212of the second injection and cutting device and a tension roller 222.

In the illustrated example, the film 53 is driven into the firstinjection and cutting device; the film 5 is held immobilized by theinjection rollers 182, 192 of the second injection and cutting device.

At the outlet of the first injection and cutting device, the film 53 isdirected toward the means 25 by the belt 36.

In FIG. 4, a first injection and cutting device includes the injectionrollers 183, 193, the pressure rollers 203, 213, and a cutting unit 233;a second injection and cutting device includes the injection rollers184, 194, the pressure rollers 204, 214, and a cutting unit 234; themeans for directing the film being unwound toward the movable guidedevice 25 are a single belt 38 the routing of which causes it to passbetween the pressure rollers of the two injection and cutting devices.

Here, it is the film 53 that is held immobilized by the injectionrollers 183, 193 of the first injection and cutting device, and the film5 is guided toward the means 25 by the belt 38.

1. A method of reloading a machine that packages products with a plasticfilm, said machine comprising injection and cutting means, which is fedwith film from a first spool, and means for storing a second spool, themethod comprising: while the first spool is in the process ofdistribution, placing the second spool in the machine and keeping a freeend of the film on the second spool ready at an entrance of theinjection and cutting means; detecting an approach of an end of the filmfrom the first spool; after having detected that the end of the film onthe first spool has reached a predetermined position in the machine,stopping an advance of the film from the first spool into the injectionand cutting means so as to leave a remaining part of the film from thefirst spool, wherein the remaining part of film from the first spoolincludes the end of the film from the first spool, and causing the freeend of the film connected to the second spool to be drawn into saidinjection and cutting means, so that said second spool becomes adistributor, and such that the film from the first spool is not fastenedto the film from the second spool; and while said second spool is in theprocess of distribution, replacing the first spool that was emptied witha new full spool and fusing a leading end of film from the new fullspool to a trailing end of the remaining part of the film from the firstspool and maintaining, at the entrance of the injection and cuttingmeans, a free end of the remaining part of film connected to said newfull spool, and utilizing film from the new full spool when the end ofthe film from the second spool, in the process of distribution, reachesa predetermined position in the machine.
 2. The method according toclaim 1, wherein the film from the first spool in the process ofdistribution is allowed to run out, and the predetermined position,which is detected, of the end of the first spool in the machine isdetermined when said end of the film from the first spool leaves theinjection and cutting means.
 3. The method according to claim 1, furthercomprising monitoring the passage of the end of the film from the firstspool to a predetermined position situated between the first spool andthe injection and cutting means; and when the passage into this positionis detected, the advance of the film from the first spool into theinjection and cutting means is stopped, in order for the remaining partof the film from the first spool to remain between said end of the filmfrom the first spool and the injection and cutting means, and the freeend of the film connected to the second spool is drawn into saidinjection and cutting means so that it becomes the distributing spool;and removing the empty first spool and putting the new full spool inplace.
 4. The method according to claim 3, wherein the detection of thepredetermined position of the end of the film from the first spool inthe process of distribution is performed twice: a first time, when anapproximate evaluation is made of the remaining length of film wound onthe first spool during the distribution, then, when a predeterminedvalue is reached, the advance of the film from the first spool into theinjection and cutting means is stopped, the second spool is placed inservice by causing the free end of the film from the second spool to bedrawn into said injection and cutting means so that the second spoolbecomes the distributor and the film from the first spool is stopped;and a second time where the remaining length of film wound on thestopped first spool is determined, after which, at least one of: a) ifthe length of film remaining on the stopped first spool is sufficient tocontinue packaging the products: the advance of the film from the secondspool into the injection and cutting means is stopped, the free end ofthe film connected to the first spool on standby is drawn into saidmeans so that said first spool becomes the distributing spool again, andthe passage is monitored of the upstream end of the film from the firstspool into said predetermined position located between the first spooland the injection and cutting means; and when the passage into thepredetermined position is reached, the advance of the film from thefirst spool into the injection and cutting means is stopped, and thesecond spool is placed in service again by causing the free end of thefilm connected to the second spool to be drawn into said injection andcutting means so that it becomes the distributing spool again; the firstspool is removed and the new full spool is installed; and the beginningof the film from the new full spool is fused to the end of the remainingpart of the film from the removed first spool, and the operator waitsuntil the remaining length of film wound on the second spool requiresanother change of spool; and b) if the remaining length of film on thestopped first spool is not enough to continue packaging the products:packaging is continued with film from the second spool until it isdetermined that the remaining length of film wound thereon requiresanother change of spool, and during this time, the end of the film fromthe first spool is drawn into the machine, in said predeterminedposition located between the first spool and the injection and cuttingmeans, and the empty first spool is removed and a new full spool is putin place; and the beginning of the film from the new full spool is fusedto the end of the remaining film from the first spool that has just beenremoved; and the preceding operations are resumed by changing over fromone spool to another.
 5. The method according to claim 4, wherein atleast one of the approximate evaluation of the length of film remainingwound on the first spool in the process of distribution, and thedetermination of the length remaining on the stopped first spool, andthe monitoring of the passage of the last part of the end of the filmfrom the first spool in the process of distribution, in the saidpredetermined position, are performed by the operator of the machine. 6.The method according to claim 4, wherein at least one of the approximateevaluation of the length of film remaining wound on the first spool inthe process of distribution, and the determination of the lengthremaining on the stopped first spool, and the monitoring of the passageof the upstream end of the film from the first spool in the process ofdistribution, in the said predetermined position, are performedautomatically.
 7. The method according to claim 4, wherein at least oneof the stopping of the first spool in the process of distribution, andthe placing in service of the new full spool, and the return to serviceof the second spool are performed by the operator of the machine.
 8. Themethod according to claim 4, wherein at least one of the stopping of thefirst spool in the process of distribution, and the placing in serviceof the new full spool, and the return to service of the second spool areperformed automatically.
 9. The method according to any of claim 3,wherein the machine has a compensation mechanism with rollercompensators between the first spool and the injection and cuttingmeans, and between the second spool and the injection and cutting means,and the predetermined position is located between the first spool andthe injection and cutting means, and an additional predeterminedposition is located between the second spool and the injection andcutting means, wherein the predetermined positions are monitored so thatthe advance from the first or second spool in the process ofdistribution is stopped when the end of the film carried by the first orsecond spool, respectively, is between the first or second spool and thecorresponding compensation mechanism.